The San Gregorio Magno lacustrine basin (Campania, southern Italy): improved characterization of the tephrostratigraphic markers based on trace elements and isotopic data

Abstract

Central–southern Italy is one of the most suitable areas in the world for tephrostratigraphic studies, owing to the numerous volcanic sources with explosive activity during the Pleistocene. This work presents a systematic investigation of the chemical (trace elements) and isotopic (Sr and Nd) compositions of the main tephra markers within lacustrine sediments of the San Gregorio Magno Basin (Campania, southern Italy). This study: (i) provides full geochemical (trace elements and isotopes) characterization of eight significant Upper Pleistocene marker layers (X‐6, X‐5, C‐22, MEGT/Y‐7, CI/Y‐5, C‐10, Y‐3, NYT/C2) widely dispersed over the Mediterranean area; (ii) proposes a new tephra marker for Marine Isotope Stage 7, dated to 240 ka; and (iii) refines the correlations of tephra levels belonging to the investigated sequence. This study highlights that in most cases the Nd isotope composition of the glass and Sr isotope composition of the coexisting minerals are more reliable than 87Sr/86Sr of the glass, and hence is more helpful as a further tool for tephrostratigraphic correlations, as recently proposed in the literature. Moreover, this study is a first step towards the construction of a complete geochemical database for future tephra investigations in the Mediterranean area. Copyright © 2019 John Wiley & Sons, Ltd.

Petrography and Mineral Chemistry of Monte Epomeo Green Tuff, Ischia Island, South Italy: Constraints for Identification of the Y-7 Tephrostratigraphic Marker in Distal Sequences of the Central Mediterranean

“…The pink field has been drawn using mineral chemistry data on Ischia trachytes and phonolites from the literature [14,19,41,43]. (B) clinopyroxene crystals and fragments separated from samples S16 [7,8] and TF-7 [2]. See Discussion for details.…”

“…[14,19,41,43]. (B) clinopyroxene crystals and fragments separated from samples S16 [7,8] and TF-7 [2]. See Discussion for details.…”

“…The most recent tephrostratigraphical and tephrochronological evidence for the occurrence of Y-7 in continental sites are the lacustrine successions of the Fucino basin located in Abruzzo, central Italy (circle 3 in Figure 1B), where the marker has been precisely dated [2], and the San Gregorio Magno basin located in Campania (circle 5 in Figure 1B) characterised by Munno and Petrosino (2007) [7] and Petrosino et al (2019) [8]. In order to test the soundness of the clinopyroxene geochemistry as a potential tool for tephra fingerprinting purposes, we selected samples from these two distal tephra layers correlated to MEGT and compared them with crystals analysed in MEGT proximal products (Figure 4).…”

“…It is the product of a complex, paroxysmal explosive eruption that occurred ≈56 ka [1,2] on the island and that resulted in caldera collapse and the wide dispersal of ash across the central Mediterranean. The MEGT is a key stratigraphic tephra marker, referred to as Y-7, and it is found in several distal continental and deep sea sedimentary records of the central Mediterranean area (Figure 1B; e.g., [2][3][4][5][6][7][8][9]), including Palaeolithic sites [10]. The total volume of erupted magma has been estimated to ≈9-15 km 3 based on caldera dimensions [11] and ≈40 km 3 based on areal distribution of proximal and distal fallout deposits [9].…”

“…The distal deposits of the MEGT [19]). (B) Map of the central Mediterranean area; numbered red circles indicate the main distal locations where the MEGT products have been either recognised or hypothesised: 1-PRAD 1-2 bore hole, Adriatic Sea [20]; 2-KET 8218 bore hole, Adriatic Sea [3]; 3-Fucino Basin, Abruzzo, Central Italy [2]; 4-Lago Grande di Monticchio, Basilicata [4,6]; 5-San Gregorio Magno basin, Campania [7,8]; 6-Oscurusciuto [10]; 7, 8, 10, 11-KET 8022, KET 8004, KET 8003, KET 8011 bore holes, Tyrrhenian Sea [3]; 9-ODP Leg 107, Site 650, Tyrrhenian Sea [21]; 12-Stromboli, Aeolian Archipelago [22]; 13, 14, 16-RC9-190, RC9-191, V10-68 bore holes, Ionian Sea [23]; 15-M25/4-11 bore hole, Ionian Sea ( [9] and references therein); 17-ODP Leg 160 Site 964 and KC01B bore holes, Ionian Sea [5,24].…”